1. Field of the Invention
The present invention relates to a novel tetragonal system tunnel-structured compound, and methods of its preparation. The novel compound is useful as a cation conductor, an ion exchanger, a catalyst or a heat resistant heat insulating material.
2. Description of the Background Art
A cation conductor is important as a material for a solid cell of ion sensor useful for electric automobiles or extra electric power for night. Heretofore, the most expected for such a cation conductor has been .beta.-alumina. However, in such .beta.-alumina, the movement of cations is in-plane i.e. two dimensional, and the cation conductivity is low. Therefore, it has been desired to develop a material having higher cation conductivity.
On the other hand, as a heat resistant heat insulating material, asbestos has been most widely used. However, asbestos is likely to form a dust during its use, and create a pollution problem. Thus, it has been desired to develop a heat insulating material which can be substituted for asbestos. Recently, potassium titanate fibers have been developed as fibers to be substituted for asbestos, by Fujiki, one of the inventors of this application, et al. (Japanese Pat. Nos. 116,459 and 116,460.) Among ceramics, the potassium titanate fibers are remarkably superior in the heat insulating property. However, they have a drawback that since their melting point is 1370.degree. C., the practically useful temperature is low at a level of up to about 1200.degree. C. Thus, a heat resistant heat insulating material having a higher melting point has been desired.